Orange jasmine as a trap crop to control Diaphorina citri

[EN] Novel, suitable and sustainable alternative control tactics that have the potential to reduce migration of Diaphorina citri into commercial citrus orchards are essential to improve management of huanglongbing (HLB). In this study, the effect of orange jasmine (Murraya paniculata) as a border trap crop on psyllid settlement and dispersal was assessed in citrus orchards. Furthermore, volatile emission profiles and relative attractiveness of both orange jasmine and sweet orange (Citrus¿×¿aurantium L., syn. Citrus sinensis (L.) Osbeck) nursery flushes to D. citri were investigated. In newly established citrus orchards, the trap crop reduced the capture of psyllids in yellow sticky traps and the number of psyllids that settled on citrus trees compared to fallow mowed grass fields by 40% and 83%, respectively. Psyllids were attracted and killed by thiamethoxam-treated orange jasmine suggesting that the trap crop could act as a `sink¿ for D. citri. Additionally, the presence of the trap crop reduced HLB incidence by 43%. Olfactometer experiments showed that orange jasmine plays an attractive role on psyllid behavior and that this attractiveness may be associated with differences in the volatile profiles emitted by orange jasmine in comparison with sweet orange. Results indicated that insecticide-treated M. paniculata may act as a trap crop to attract and kill D. citri before they settled on the edges of citrus orchards, which significantly contributes to the reduction of HLB primary spread.This work was supported by Fund for Citrus Protection (Fundecitrus) and by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) (Proc. 2015/07011-3). We thank Moacir Celio Vizone, Felipe Marinho Martini and Joao Pedro Ancoma Lopes for technical support with experiments. Furthermore, we thank Cambuhy Agricola Ltda. and University of Araraquara (Uniara) for providing the areas in which the field experiments were performed. 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beta-caryophyllene emitted from a transgenic Arabidopsis or chemical dispenser repels Diaphorina citri, vector of Candidatus Liberibacters

[EN] Production of citrus, the main fruit tree crop worldwide, is severely threatened by Huanglongbing (HLB), for which as yet a cure is not available. Spread of this bacterial disease in America and Asia is intimately connected with dispersal and feeding of the insect vector Diaphorina citri, oligophagous on rutaceous host plants. Effective control of this psyllid is an important component in successful HLB management programs. Volatiles released from the non-host guava have been shown to be repellent to the psyllid and to inhibit its response to citrus odour. By analysing VOC emission from guava we identified one volatile compound, (E)-ß-caryophyllene, which at certain doses exerts a repellent effect on D. citri. Non-host plant rejection mediated by (E)-ß-caryophyllene is demonstrated here by using Arabidopsis over-expression and knock-out lines. For the first time, results indicate that genetically engineered Arabidopsis plants with modified emission of VOCs can alter the behaviour of D. citri. This study shows that transgenic plants with an inherent ability to release (E)-ß-caryophyllene can potentially be used in new protection strategies of citrus trees against HLB.We thank Dr. Pedro Serra (IBMCP, Valencia, Spain) for his help with statistical analysis, and Prof. Dr. Luiz A.B. de Moraes (Chemistry Department, FFCLRP, USP, Riberao Preto, Brazil) and Prof. Dr. Edson Rodrigues Filho (LaBioMMi, Chemistry Department, UFSCar, Sao Carlos, Brazil) for the use of GC-MS equipment. Use of the Citrus Germplasm Bank (IVIA, Valencia, Spain) is gratefully acknowledged. This work was funded by the Fundo de Defesa da Citricultura (Fundecitrus) and FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo, 2015/0711-3). In memoriam of Prof. J.M.Bove.Alquézar-García, B.; Linhares Volpe, HX.; Magnani, RF.; De Miranda, MP.; Santos, MA.; Wulff, NA.; Simoes Bento, JM.... (2017). beta-caryophyllene emitted from a transgenic Arabidopsis or chemical dispenser repels Diaphorina citri, vector of Candidatus Liberibacters. Scientific Reports. 7. https://doi.org/10.1038/s41598-017-06119-wS7Bove, J. M. H. A destructive, newly-emerging, century-old disease of citrus. J. Plant Pathol. 88, 7–37 (2006).Gottwald, T. R. Current Epidemiological Understanding of Citrus Huanglongbing. Annu. Rev. Phytopathol 48, 119–39 (2010).FAOSTAT. Food and Agriculture Organization of the United Nations. Available at: http://faostat3.fao.org/home/E (Accessed: 4th July 2016).Hodges, A. W., Rahmani, M., Stevens, T. J. & Spreen, T. H. Economic impacts of the florida citrus industry final sponsored project report to the Florida department of citrus. 1–39 (2014).Beattie, G. A. C. et al. 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Citrus flush shoot ontogeny modulates biotic potential of <i>Diaphorina citri</i>

<div><p>The biology and behaviour of the psyllid <i>Diaphorina citri</i> Kuwayama (Hemiptera: Sternorrhyncha: Liviidae), the major insect vector of bacteria associated with huanglongbing, have been extensively studied with respect to host preferences, thermal requirements, and responses to visual and chemical volatile stimuli. However, development of the psyllid in relation to the ontogeny of immature citrus flush growth has not been clearly defined or illustrated. Such information is important for determining the timing and frequency of measures used to minimize populations of the psyllid in orchards and spread of HLB. Our objective was to study how flush ontogeny influences the biotic potential of the psyllid. We divided citrus flush growth into six stages within four developmental phases: emergence (V1), development (V2 and V3), maturation (V4 and V5), and dormancy (V6). <i>Diaphorina citri</i> oviposition and nymph development were assessed on all flush stages in a temperature controlled room, and in a screen-house in which ambient temperatures varied. Our results show that biotic potential of <i>Diaphorina citri</i> is not a matter of the size or the age of the flushes (days after budbreak), but the developmental stage within its ontogeny. Females laid eggs on flush V1 to V5 only, with the time needed to commence oviposition increasing with the increasing in flush age. Stages V1, V2 and V3 were most suitable for oviposition, nymph survival and development, and adult emergence, which showed evidence of protandry. Flush shoots at emerging and developmental phases should be the focus of any chemical or biological control strategy to reduce the biotic potential of <i>D</i>. <i>citri</i>, to protect citrus tree from Liberibacter infection and to minimize HLB dissemination.</p></div